Field Test: the M Mobility System

(from May ’00 Sin City Screamer, BMW CCA chapter newsletter)

Those of you enjoying your M Roadsters and E39 M5s may have to explain to sensible folks why your expensive BMW doesn’t even have a spare tire. I’ve tried to suggest the missing spare stems from BMW’s environmental concerns: Why equip a car with 25% more tires than can touch the ground at once, only to end up in smoldering landfills?

Of course, that’s not the reason. The M5 doesn't have a spare because front and wheels are seriously disparate in width, which along with directional tires would make a single spare less than optimum. And the M5 quad exhaust includes four separate mufflers just ahead of the chrome tips. The mufflers and the large rear trunk-mounted M5 battery consume all the space where the spare tire well is on the 528i/540i.

In lieu of a spare tire and a jack, the M5 and M Roadster come with the "M Mobility System," a combination compressor/sealant dispenser the size of a large cereal box that plugs into the cigarette lighter. The kit includes plastic goggles and latex gloves. M cars so equipped also include BMW Roadside Assistance, so carry a cell phone and you won’t have to get your hands dirty.

I got to test the system on a late Sunday afternoon drive from Vegas to Reno, a distance of about 470 miles. Of course, I must note that all posted speed limits were observed. (I might say that I observed them and then multiplied them by some factor, but that would not only be self-incriminating, it would imply that BMW AG, BMW NA, BMW CCA and the Sin City Chapter condone speeding, which they do not. If BMW wanted you to speed, don’t you think they’d give you a spare tire?)

So, I was making merely excellent time when I stopped for fuel in Tonopah at about 6 p.m., roughly halfway to Reno. Now, Tonopah is a tiny blip of a town, some closed storefronts, one Best Western, but maybe one of the larger spots on this desolate route. Just as I pulled into the gas station the dreaded "TIRE DEFECT" message appeared on the dash. A nail was embedded into my left rear 275/35ZR18 Michelin Pilot Sport, hissing slowly. I extracted the M Mobility System from the trunk, donned goggles and gloves, and hooked up the hoses. At first, there didn’t seem to be any sealant or pressure. After about ten minutes I jiggled the hoses around a little and the white sealant started to pump into the tire. After a few minutes the sealant was all gone and the nail still hissed at me. (You're supposed to leave the object in the tire if possible.)

I then called BMW Roadside Assistance and "Kathy" took my VIN, location and cell phone number. (I also had two cell phones with me, and my AT&T Wireless/Nokia phone worked in Tonopah while my Nextel/Motorola was useless.) I told her I needed to get to Reno, which happened to be the location of the nearest BMW dealer, and there were no rental cars in Tonopah. A few minutes later she called me back, gave me the number of the towing outfit that was going to flatbed my car and me to Reno (which she thought was 162 miles away, instead of the actual 242miles). About 20 minutes later, a tow truck showed, but it was the wrong truck, not geared for the highway. The driver/owner said his road truck was on its way back from Fallon, several hours away. After checking out the M5, he gave me his number, said we’d get to Reno, but it would be very late, and left.

The tire wasn't getting much flatter, though it was still hissing, so I drove the length of the town to a closed Chevron station with an air hose outside. I used my trusty digital BMW tire pressure gauge and filled the tire to spec (48 psi rear) and to my surprise, it held. I checked the other tires, which were all fine, and checked Mr. Defect again, and it was still round and full. I decided to go for it, and called the tow truck guy to let him know. He kindly gave me the cell phone number of his driver on the road from Fallon, just in case.

By now I had lost over two hours and it was dark. Now, the M Mobility System is supposed to be for emergency use, and tires so repaired are supposed to be kept below 50 mph (at 35 psi). I quickly realized that the sealant had apparently congealed asymmetrically, because there was a terrible vibration at just above 60 mph. (I noticed it was a little smoother at 80 mph but I didn't dare risk high-speed travel; I’m no speeder, you know.) So, for the first time, I got to use the cruise control in the M5. Set it for 60 mph, and just steered the rest of the way, 242 miles at 60 mph with a spiked tire.

Next morning, I called Tire Rack, one of the largest mail order distributors. Though headquartered in Indiana, they happen to have a warehouse in Reno/Sparks. I arranged to pick up the tire in Sparks, and had it installed at a neighborhood Big O Tire store. They did a great job, and also patched the nailed Michelin. The tire was $306 plus tax, and the Big O services came to about $24. The job was completed when Bill Pearce BMW in Reno replaced the sealant canister in my cereal box. No charge.

All in all, an inconvenience, but the system worked, both the M Mobility System and BMW Roadside Assistance. Wonder if BMW will spring for the tire, seeing as how I saved them a 242 mile towing bill?


Richard Scheer